<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>结构性伪类选择器 root</title>
    <style>
        * {
            margin: 0
        }
        /* html 根元素 */
        :root {
            background: orange;
        }
    </style>
</head>

<body>
    <div>:root选择器的演示</div>
</body>

</html>